docs: def get_stim(self, type_, return_all=False):
          ''' Returns component elements of the specified type.
  
          Args:
              type_ (str or Stim class): the desired Stim subclass to return.
              return_all (bool): when True, returns all elements that matched the
                  specified type as a list. When False (default), returns only
                  the first matching Stim.
  
          Returns:
              If return_all is True, a list of matching elements (or an empty
              list if no elements match). If return_all is False, returns the
              first matching Stim, or None if no elements match.
          '''
          if isinstance(type_, string_types):
              type_ = _get_stim_class(type_)
          matches = []
          for s in self.elements:
              if isinstance(s, type_):
                  if not return_all:
                      return s
                  matches.append(s)
          if not matches:
              return [] if return_all else None
          return matches